The present invention generally relates to systems and apparatus of underground pipe, and, more particularly, to a fluid-filled jacket for concrete pipe.
Steel reinforced concrete (R/C) pipes are routinely used in underground applications such as culverts, storm-water drains, and sanitary sewers. Concrete is well suited to carry compressive stresses, but not tensile stresses because tensile strength of concrete is an order of magnitude smaller than the compressive strength of concrete. Consequently, some buried concrete pipes may exhibit significant tensile cracking due to circumferential bending moments that are caused by non-uniform soil pressures acting on the pipe periphery. Some concrete pipe manufacturers compensate for concrete's tensile weakness by placing circumferential rows of reinforcing steel in the concrete wall to sustain the tensile load when the concrete cracks. The cracked portion of the concrete wall is structurally useless except as a matrix to contain the steel reinforcement. Hence, as currently designed, traditional concrete pipes have two economic shortcomings: the need of substantial reinforcing steel and the need of thicker concrete walls to account for concrete cracking.
As can be seen, there is a need for an improved system and apparatus of underground pipe that does not transmit bending moments to the concrete pipe.